December 29, 1922] 



SCIENCE 



741 



This fact leads, under proper conditions, to 

 an uaiequal distnibuition of 'the diffusible crystal- 

 loidal ions beti^een a protein solution and an 

 outside aqueous solution; or 'between a protein 

 gel and an aqueous solution. In this distribu- 

 tion the total concentration of crystalloidal ions 

 as always greater inside the protein solution or 

 inside a gel than in the surrounding aqueous 

 solution. This is the cause of the colloidal be- 

 havior of protein solutions and protein gels. 

 Measurements of membrane potentials have 

 shown that this excess of the ooneentration of 

 crystalloidal ions inside over the concentration 

 of tihe crystalloidal ions outside the protein 

 solution or the gel, and consequently all the 

 effects of electrolytes on osmotic pressure, 

 swelling and viscosity of proteins, can be cal- 

 culated "with a satisfactory degree of accuracy 

 from Donnan's equilibrium equation, which is 

 not an empirical but a rationalistic mathe- 

 matdcal formula. We can therefore state that 

 it is possible to explain the coilloidal ibehavior 

 of proteins quantitatively on the basis of a 

 rationalistic mathematical formula. What ap- 

 peared at first as a new chemistry, the so-called 

 colloid chemistry, now seems to have been only 

 an overlooked equilibrium condition of classical 

 chemistry; at least as far as the proteins are 

 concerned. The oversight was due to two facts, 

 first, to the failure of colloid chemists to 

 measure the hydrogen ion concentration of 

 their solutions, which happens to be the chief 

 variable in the case, and second, to their neglect 

 of measui'ing and taking into consideration the 

 membrane potentials of protein solutions and 

 protein gels, which furnish the proof that the 

 theory of membrane equilibria must be used to 

 explain the colloidal behavior of proteins. 



Jacques Loeb 

 The Eockefellee Institute 

 POE Medical Eeseaech, 

 New Yoek 



THE AWARD OF THE HENRY 

 DRAPER MEDAL 



The Henry Draper medal for 1921, awarded 

 by the National Academy of Sciences to Pix)- 

 fessor Henry Norris Russell, professor of as- 

 tronomy at Princeton Univei-sity, was pre- 



sented to him by Dr. C. G. A'bbot, assistant 

 director of the Smithsonian Institution at the 

 annual dinner in New York City on November 

 15. Dr. Abbot spoke as foUows : 



The brilliaiit and penetrating insdghjt of Dr. 

 Henry Norris Kiissell, of Princeton University, 

 hais led dn recent years to a development of as- 

 tronomy so rapid tliait it has proved tlius far 

 impossible to publish really up-ito-date text-books 

 on the subject. Before the mannsBript of a test 

 on lastronomy can be prepared, mucih less carried 

 through the press, new knowledge renders the 

 treatment stale. 



Dr. Eussell has made basic contributions to the 

 great problem of SiteUar evolution. He saw 

 clearly .that the brigihtness of a star as we see it 

 depends on several fadtors. First, there is the 

 inftrinsic brightness of the istar as a source of 

 light. What the tallow candle is to the electric 

 arc, so one sitar niiay be to amortiher in the bright- 

 ness of its shining surface. Secondly, the total 

 amount of light whicli a star sends out depends 

 upon its diameter. Quite recently it has been 

 sliowQ, for instaji'Ce, that the atar Alpha Orionds 

 is three hundred times the diameter of the sun, 

 and aceoirdingly its cross-iseetiiomal area is ninety 

 thousand times the oross-seetional area of the sun. 

 Hence, if they were of equal surface brighitness, 

 the star Alpha Orionis would send out ninety 

 thousand times as much light as the sun. In the 

 third place, the brightness of the star depends 

 upon its distajnce from the earth laad falls off as 

 the square of that dLsttance. Thus, the sun, which 

 is so near tliat it takes light eight minutes to 

 come from it, being about two hundred thousand 

 times as near as the nest nearest sta-r which takes 

 light three or four years to reach the earth will 

 appear forty miillion times brighter on that ac- 

 count. 



With these loonditions in mind, Dr. Eussell, in 

 collaboration mth Dr. Hinks, of England, began 

 by the application of a new phottographic method 

 of determiaing the distance of stars, and in 1910 

 published the resmllts showing the approximate 

 distance of 55 istars. With this and other such 

 information which had been laboriously acquired 

 by others, he was able to show that the red stars 

 evidently must fall into two classes: one class, 

 sending out very much more light than our sun, 

 and another sending out very much less, and that 

 beitween these two very widely separated extremes 

 there are no red stars intervening. 



Going on, he applied the, until then little used, 

 knowledge of the eclipsing variable stars mth the 



